Compared to a placebo, saw palmetto capsules, pictured above, do not alleviate urinary problems related to an enlarged prostate, even when men take up to three times the standard daily dose.

The fruit of the saw palmetto tree does not relieve symptoms of an enlarged prostate, even when men take the herbal supplement in very high doses, shows a study published in the Journal of the American Medical Association.

Results of the trial may settle an ongoing debate over the effectiveness of saw palmetto for benign prostatic hyperplasia (BPH), where the prostate is enlarged. Many older US men take saw palmetto extract in an attempt to reduce BPH symptoms, including frequent urination and a sense of urgency. Earlier studies of the supplement have produced conflicting results, and none has evaluated the benefits of saw palmetto in high doses.

In the current study, however, men took up to three times the standard dose of saw palmetto.

No better than a placebo

“Now we know that even very high doses of saw palmetto make no difference,” says co-author Gerald Andriole Jr., MD, chief of urologic surgery at Washington University School of Medicine and Barnes-Jewish Hospital. “Men should not spend their money on this herbal supplement because it clearly does not work any better than a placebo.”

The multi-center study involved more than 300 men ages 45 and older who had moderate symptoms suggestive of an enlarged prostate. The men were randomly selected to receive a daily dose of saw palmetto extract, beginning at 320 milligrams, or an identical-looking placebo.

After 24 weeks, the saw palmetto dosage was increased to 640 milligrams a day, and after another 24 weeks, to 960 milligrams a day— triple the standard dose. Men took saw palmetto or a placebo for nearly 17 months.

The researchers found that among men who took saw palmetto, prostate problems improved slightly but not more than in men taking a placebo. Saw palmetto had no greater effect than the placebo on BPH symptoms as well as other conditions related to an enlarged prostate such as waking at night to urinate and bladder control.

Consistently ranked a top medical school for research, Washington University School of Medicine is also a catalyst in the St. Louis biotech and startup scene. Our community includes recognized innovators in science, medical education, health care policy and global health. We treat our patients and train new leaders in medicine at Barnes-Jewish and St. Louis Children's hospitals, both ranked among the nation’s best hospitals and recognized for excellence in care.